Allyl propargyl ethers undergo cobalt-mediated cycloisomerization reactions to form dihydrofurans in good yield and with excellent diastereoselectivity. The reaction is proposed to proceed by way of an allylic C-H activation and a formal 5-endo-dig cyclization. The reaction works with a range of allylpropargyl ether substrates. / 1,6-Enynes and allyl propargyl ethers undergo a cobalt-catalyzed formal 5-endo-dig cyclization to form vinyl cyclopentenes and dihydrofurans, respectively. The use of equimolar amounts of dicobalt octacarbonyl and trimethyl phosphite affords optimum yields and improved selectivity for cycloisomerization vs. alkene isomerization. / The utility of the cycloisomerization reaction is exemplified through the synthesis of the bis-tetrahydrofuran core of the annonaceous acetogenins. A key feature of the approach centers on the cycloisomerization reaction for the installation of two of the four stereocenters found in the THF-subunit. / An approach towards the total synthesis of Stolonoxide C is described. The mono-THF subunit is synthesized from the corresponding cobalt catalyzed cycloisomerization of an appropriate allylpropargyl ether.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.85112 |
| Date | January 2005 |
| Creators | Ajamian, Alain |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002227795, proquestno: AAINR12792, Theses scanned by UMI/ProQuest. |
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